Measurements of saturated-liquid densities for isobutane at T = (280 to 407) K

Ten measurements of the saturated-liquid density for isobutane were obtained by means of a metal-bellows variable volumometer at T = (280 to 407) K. The mole fraction purity of the isobutane used in the measurements was 0.9999. For the determination of the saturation boundary at each temperature for isobutane, we measured the density data at intervals of about 12 kPa very close to the saturation boundary. The expanded uncertainties (k = 2) in temperature, pressure, and density measurements have been estimated to be less than 3 mK, less than 0.8 kPa, and 0.08%, respectively. After such measurements had been completed, the saturated-liquid density results for each temperature were determined as the point of intersect between the isotherm and our previously determined vapour pressure value. The expanded uncertainties (k = 2) in the present saturated-liquid density data have also been estimated to be less than 0.08%, except the uncertainty of the saturated-liquid density data at T = 400 K being 0.09% (0.31 kg · m⁻³). Based on the present measurements as input data, the saturated-liquid density correlation were also provided for the systematic comparisons between the present measurements and the literature data.